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The pitfalls of ectomycorrhizal microcosms: lessons learnt for future success

Summary

Researchers attempted to test whether fungal networks could guide plant roots through physical obstacles by growing pine seedlings with fungi in specialized maze chambers. While the fungi successfully colonized the roots 88% of the time, the roots grew unexpectedly large and the experimental apparatus failed, preventing them from testing their hypothesis. The study provides valuable lessons about what went wrong and recommendations to improve this type of experiment for future researchers studying how fungi and plants interact.

Background

Ectomycorrhizal fungi are known to support host plants by facilitating nutrient acquisition and stress resistance. However, whether these fungi convey structural information about soil properties to guide root growth remains unexplored. Classical microcosm experiments have been used to study mycorrhizal symbioses but detailed methodological information is often insufficient for accurate replication.

Objective

The study aimed to investigate whether ectomycorrhizal hyphae could guide root growth in response to physical obstacles using Pinus sylvestris and Suillus granulatus in U-shaped silicone maze microcosms. The researchers hypothesized that fungal hyphae would grow faster than roots and signal obstacles, causing inoculated plants to develop more lateral roots to avoid the maze compared to uninoculated controls.

Results

Ectomycorrhizal colonization was successful in 88% of inoculated seedlings. However, extensive unexpected root growth occurred in both treatments, and the Perspex plates began bending outward, compromising substrate integrity. No significant hyphal networks developed as expected from classical studies, and no significant differences were observed between inoculated and control plants in any measured parameters after 4 or 6 weeks.

Conclusion

The original hypothesis could not be tested due to technical failures and excessive root growth rendering the system unsuitable. The authors provide detailed recommendations for future ectomycorrhizal microcosm experiments, including using cloned seedlings, rigorous substrate testing, improved microcosm design, and preliminary testing protocols. Despite negative results, the study contributes valuable methodological insights for improving reproducibility in mycorrhizal research.
  • Published in:Plant Signaling & Behavior,
  • Study Type:Experimental Study - Negative Results Report,
  • Source: 10.1080/15592324.2025.2527378, PMID: 40621791
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